TWI534583B - Low-dropout voltage regulator - Google Patents

Description

Low dropout regulator

This invention relates to a voltage regulator and, more particularly, to a low dropout voltage regulator.

In recent years, low-dropout voltage regulator (LDO) has become the mainstream of power supply circuits due to its low noise, small size, low cost, etc., and is widely used in various electronic products. In operation, the low dropout regulator converts the input voltage to an output voltage for use by the back end load. However, in the no-load state, the existing low-dropout regulator still has a plurality of current paths that are conducted to the ground, thereby causing the existing low-dropout regulator to have a large standby current. Thereby increasing the power consumption of the existing low dropout regulator.

The invention provides a low-dropout voltage regulator, which uses a control signal generated by a differential amplifier to control a feedback circuit and a signal generation circuit, thereby reducing a standby current of a low-dropout regulator, thereby reducing a low-dropout regulator. Power consumption.

The low dropout regulator of the present invention has a voltage output terminal and includes a first differential amplifier, a power switch, an impedance component, a second differential amplifier, a feedback circuit and a signal generating circuit. The first differential amplifier generates a first control signal according to the reference voltage and the feedback voltage. The power switch receives the input voltage and is controlled by the first control signal. The impedance element is electrically connected between the power switch and the voltage output. The second differential amplifier is electrically connected to both ends of the impedance element and generates a second control signal. The feedback circuit determines whether to generate a feedback voltage according to the second control signal. The signal generating circuit determines whether to generate a reference voltage according to the second control signal.

In an embodiment of the invention, the second differential amplifier has an input offset voltage. In addition, when the voltage output terminal is electrically connected to the load, the second differential amplifier switches the second control signal to the first level according to the voltage across the impedance element. When the voltage output terminal is not connected to the load electrical property, the second differential amplifier switches the second control signal to the second level according to the input offset voltage.

Based on the above, the low-dropout regulator of the present invention controls the power switch by using the first control signal generated by the first differential amplifier, and controls the feedback circuit and the signal generation by using the second control signal generated by the second differential amplifier. Circuit. Thereby, the standby current of the low dropout regulator can be effectively reduced, thereby reducing the power consumption of the low dropout regulator.

The above described features and advantages of the invention will be apparent from the following description.

10‧‧‧ Low dropout regulator

101‧‧‧voltage output

110, 140‧‧‧Differential Amplifier

120‧‧‧Power switch

130‧‧‧ impedance components

150‧‧‧Return circuit

160‧‧‧Signal generation circuit

151, 161‧‧ ‧ switch

162‧‧‧Voltage generator

R1~R3‧‧‧ resistor

PT1, PT2‧‧‧ current path

20‧‧‧ load

VIN‧‧‧ input voltage

VO‧‧‧ output voltage

VR‧‧‧reference voltage

VF‧‧‧ feedback voltage

CT1, CT2‧‧‧ control signals

310‧‧‧Ideal amplifier

320‧‧‧Input offset voltage

TM31‧‧‧ positive input

TM32‧‧‧Negative input

TM33‧‧‧ output

410‧‧‧ input level

420‧‧‧Output

430‧‧‧current source

MN41~MN43‧‧‧N type transistor

MP41, MP42‧‧‧P type transistor

VD‧‧‧Power supply voltage

1 is a circuit diagram of a low dropout voltage regulator according to an embodiment of the invention.

2 is a circuit diagram of a low dropout regulator in an unloaded state in accordance with an embodiment of the present invention.

3 is an equivalent circuit diagram of a differential amplifier in accordance with an embodiment of the present invention.

4 is a circuit diagram of a differential amplifier in accordance with an embodiment of the present invention.

1 is a circuit diagram of a low dropout voltage regulator according to an embodiment of the invention. As shown in FIG. 1, the low dropout regulator 10 has a voltage output 101 to provide an output voltage VO to the load 20. Further, the low dropout voltage regulator 10 includes a differential amplifier 110, a power switch 120, an impedance element 130, a differential amplifier 140, a feedback circuit 150, and a signal generating circuit 160. The positive input terminal of the differential amplifier 110 is electrically connected to the signal generating circuit 160 to receive the reference voltage VR. The negative input terminal of the differential amplifier 110 is electrically connected to the feedback circuit 150 to receive the feedback voltage VF. In addition, the differential amplifier 110 generates the control signal CT1 according to the reference voltage VR and the feedback voltage VF.

The power switch 120 receives the input voltage VIN and is controlled by the control signal CT1. The impedance element 130 is electrically connected between the power switch 120 and the voltage output terminal 101. The positive input terminal of the differential amplifier 140 is electrically connected to the first end of the impedance element 130, and the negative input terminal of the differential amplifier 140 is electrically connected to the second end of the impedance element 130. That is, the differential amplifier 140 is electrically connected to both ends of the impedance element 130. In addition, The differential amplifier 140 is configured to generate a control signal CT2 to control the feedback circuit 150 and the signal generating circuit 160. For example, the feedback circuit 150 can determine whether to generate the feedback voltage VF according to the control signal CT2, and the signal generation circuit 160 can determine whether to generate the reference voltage VR according to the control signal CT2.

Further, the feedback circuit 150 includes a switch 151, a resistor R1, and a resistor R2. The first end of the switch 151 is electrically connected to the voltage output terminal 101, and the control end of the switch 151 is electrically connected to the output end of the differential amplifier 140 to receive the control signal CT2. The first end of the resistor R1 is electrically connected to the second end of the switch 151. The first end of the resistor R2 is electrically connected to the second end of the resistor R1, and the second end of the resistor R2 is electrically connected to the ground. Furthermore, the signal generating circuit 160 includes a switch 161 and a voltage generator 162. The first end of the switch 161 receives the input voltage VIN, the second end of the switch 161 is electrically connected to the voltage generator 162, and the control end of the switch 161 is electrically connected to the output end of the differential amplifier 140 to receive the control signal CT2. In addition, the impedance element 130 can be, for example, a resistor R3, and the resistor R3 is electrically connected between the two input terminals of the differential amplifier 140.

In operation, the low dropout regulator 10 is electrically coupled to the load 20 via the voltage output 101 and drives the load 20 through the output voltage VO. For example, as shown in FIG. 1, when the voltage output terminal 101 is electrically connected to the load 20, the negative input terminal of the differential amplifier 110 can be turned on to the ground through the feedback circuit 150, and the differential amplifier 110 is positive. The input is in a floating state, which in turn causes the differential amplifier 110 to switch the control signal CT1 to a first level (eg, a high level). In addition, the power switch 120 is turned on in response to the control signal CT1 having the first level. The first end and the second end, in turn, generate a current flowing through the impedance element 130, and cause the two ends of the impedance element 130 to generate respective voltages.

The differential amplifier 140 switches the control signal CT2 to a first level (eg, a high level) in accordance with the voltage across the impedance element 130. For example, when a current flows through the impedance element 130, a voltage difference is generated across the impedance element 130. In addition, the voltage difference formed by the impedance component 130 causes the level of the positive input terminal of the differential amplifier 140 to be higher than the level of the negative input terminal of the differential amplifier 140, thereby causing the differential amplifier 140 to switch the control signal CT2 to the first level. (for example, high level).

Furthermore, the feedback circuit 150 generates a feedback voltage VF in response to the control signal CT2 having the first level. For example, the feedback circuit 150 turns on the switch 151 in response to the control signal CT2 having the first level. Thereby, the current path PT1 will be formed, and the output voltage VO will be transmitted through the switch 151 to the resistor R1. In addition, the resistor R1 and the resistor R2 divide the output voltage VO to generate a feedback voltage VF. In other words, when the voltage output terminal 101 is electrically connected to the load 20, the feedback circuit 150 can turn on the switch 151 according to the control signal CT2 to generate the feedback voltage VF through the second end of the resistor R1.

On the other hand, the signal generating circuit 160 generates the reference voltage VR in response to the control signal CT2 having the first level. For example, the signal generating circuit 160 turns on the switch 161 in response to the control signal CT2 having the first level. Thereby, the current path PT2 will be formed, and the input voltage VIN can be transmitted to the voltage generator 162 through the switch 161. Further, the voltage generator 162 converts the input voltage VIN from the switch 161 into a reference voltage VR. In other words, when the voltage output terminal 101 is electrically connected When the load 20 is received, the signal generating circuit 160 can turn on the switch 161 according to the control signal CT2, so that the voltage generator 162 generates the reference voltage VR according to the input voltage VIN from the switch 161.

In addition, the feedback circuit 150 adjusts the feedback voltage VF according to the output voltage VO, and the differential amplifier 110 adjusts the current generated by the power switch 120 according to the feedback voltage VF and the reference voltage VR, thereby causing the low-dropout regulator 10 to Produces a stable output voltage VO. In other words, in the case of a load, the differential amplifier 140 switches the control signal CT2 to the first level, so that the feedback circuit 150 generates the feedback voltage VF and causes the signal generating circuit 160 to generate the reference voltage VR. In addition, the low dropout regulator 10 adjusts the current of the power switch 120 according to the voltage VF and the reference voltage VR to convert the input voltage VIN into a stable output voltage VO.

It should be noted that when the voltage output terminal 101 is electrically disconnected from the load 20, that is, when the low dropout voltage regulator 10 is in a no-load state, the differential amplifier 140 switches the control signal CT2 to the second level. At this time, the feedback circuit 150 will stop generating the feedback voltage VF, and the signal generation circuit 160 will stop generating the reference voltage VR. In other words, in the case of no load, the low-dropout regulator 10 can disable the feedback circuit 150 and the signal generating circuit 160 by using the control signal CT2, thereby effectively reducing the standby current of the low-dropout regulator 10. Thereby, the power consumption of the low dropout regulator 10 is effectively reduced.

For example, FIG. 2 is a circuit diagram of a low dropout regulator in an unloaded state in accordance with an embodiment of the present invention. As shown in FIG. 2, there is an input offset voltage between the two input terminals of the differential amplifier 140. In addition, in In the absence of load, the current flowing through the impedance element 130 will be greatly reduced, thereby causing the voltage difference generated by the impedance element 130 to be less than the input offset voltage of the differential amplifier 140. At this time, the level of the positive input terminal of the differential amplifier 140 will be lower than the level of the negative input terminal of the differential amplifier 140, thereby causing the differential amplifier 140 to switch the control signal CT2 to the second level (eg, low level).

In other words, in the case of no load, that is, when the voltage output terminal 101 is not connected to the load power, the differential amplifier 140 switches the control signal CT2 to the second level according to the input offset voltage (for example, a low level). ). In addition, the feedback circuit 150 stops generating the feedback voltage VF in response to the control signal CT2 having the second level. For example, the feedback circuit 150 will not turn on the switch 151 in response to the control signal CT2 having the second level. Thereby, the feedback circuit 150 will not be able to form the current path PT1 as shown in FIG. 1, thereby stopping the supply of the feedback voltage VF. In addition, as the switch 151 is not turned on, the voltage output terminal 101 is switched to the floating state, thereby causing the power switch 120 to be incapable of being turned on.

Furthermore, the signal generating circuit 160 stops generating the reference voltage VR in response to the control signal CT2 having the second level. For example, the signal generation circuit 160 may not turn on the switch 162 in response to the control signal CT2 having the second level. Thereby, the signal generating circuit 160 will not be able to form the current path PT2 as shown in FIG. 1, thereby stopping the generation of the reference voltage VR. In other words, in the case of no load, the low-dropout regulator 10 can cut off the current path PT1 and the current path PT2 as shown in FIG. 1 by using the control signal CT2, thereby effectively reducing the standby current of the low-dropout regulator 10. .

In order to make the general knowledge in the field, the difference amplifier can be better understood. An input offset voltage of 140, and FIG. 3 is an equivalent circuit diagram of a differential amplifier according to an embodiment of the present invention. As shown in FIG. 3, the differential amplifier 140 is coupled to an input voltage of a positive input terminal of an ideal amplifier 310. Further, the differential amplifier 140 has a positive input terminal TM31, a negative input terminal TM32, and an output terminal TM33. When the positive input terminal TM31 of the differential amplifier 140 is shorted to the negative input terminal TM32, the differential amplifier 140 generates a control signal CT2 having a second level based on the input offset voltage 320.

It is worth mentioning that those skilled in the art can form the required input offset voltage 320 by adjusting the size of the internal components of the differential amplifier 140. For example, FIG. 4 is a circuit diagram of a differential amplifier in accordance with an embodiment of the present invention. As shown in FIG. 4, the differential amplifier 140 includes an input stage 410, an output stage 420, and a current source 430. The input stage 410 includes an N-type transistor MN41 and an N-type transistor MN42. Further, the control terminal of the N-type transistor MN41 is used as the positive input terminal TM31 of the differential amplifier 140, and the control terminal of the N-type transistor MN42 is used as the negative input terminal TM32 of the differential amplifier 140. Furthermore, the size (eg, aspect ratio) of the N-type transistor MN41 is smaller than the size (eg, aspect ratio) of the N-type transistor MN42 to form the input offset voltage 320. The output stage 420 is electrically connected to the first end of the N-type transistor MN41 and the first end of the N-type transistor MN42, and provides the control signal CT2 through the output terminal TM33. The current source 430 is electrically connected to the second end of the N-type transistor MN41 and the second end of the N-type transistor MN42.

Specifically, the output stage 420 includes a P-type transistor MP41 and a P-type transistor MP42, and the current source 430 includes an N-type transistor MN43. Among them, P type electricity The first end of the crystal MP41 is electrically connected to the first end of the N-type transistor MN41, the second end of the P-type transistor MP41 receives the power supply voltage VD, and the control end of the P-type transistor MP41 is electrically connected to the P-type transistor MP42. The console. The first end of the P-type transistor MP42 is electrically connected to the first end of the N-type transistor MN42, the second end of the P-type transistor MP42 receives the power supply voltage VD, and the control end of the P-type transistor MP42 is electrically connected to the first end Sexual connection. The first end of the N-type transistor MN43 is electrically connected to the second end of the N-type transistor MN41 and the second end of the N-type transistor MN42, and the second end of the N-type transistor MN43 is electrically connected to the ground, and N The control end of the type transistor MN43 is electrically connected to the first end.

In addition, in the embodiment of FIG. 4, the N-type transistors MN41 to MN43 and the P-type transistors MP41 to MP42 are realized by a metal oxide semiconductor transistor (Metal Oxide Semiconductor transistor). Therefore, in the embodiment of FIG. 4, the first end, the second end, and the control end of the N-type transistors MN41-MN43 and the P-type transistors MP41-MP42 are respectively the drain and source of the MOS transistor. Gate. In addition, in another embodiment, the N-type transistors MN41-MN43 and the P-type transistors MP41-MP42 may also be implemented by bipolar transistors, respectively.

In summary, the low dropout regulator of the present invention utilizes a differential amplifier to generate a control signal. In addition, the feedback circuit determines whether to generate the feedback voltage according to the control signal, and the signal generation circuit determines whether to generate the reference voltage according to the control signal. Therefore, under no load, the low dropout regulator can cut off the current path in the feedback circuit and the signal generating circuit, thereby effectively reducing the standby current of the low dropout regulator, thereby reducing the low dropout stability. The power consumption of the press. In addition, there is a negative In the case of a load, the low dropout regulator can also quickly restore power.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and any one of ordinary skill in the art can make some changes and refinements without departing from the spirit and scope of the present invention. The scope of the invention is defined by the scope of the appended claims.

10‧‧‧ Low dropout regulator

101‧‧‧voltage output

110, 140‧‧‧Differential Amplifier

120‧‧‧Power switch

130‧‧‧ impedance components

150‧‧‧Return circuit

160‧‧‧Signal generation circuit

151, 161‧‧ ‧ switch

162‧‧‧Voltage generator

R1~R3‧‧‧ resistor

PT1, PT2‧‧‧ current path

20‧‧‧ load

VIN‧‧‧ input voltage

VO‧‧‧ output voltage

VR‧‧‧reference voltage

VF‧‧‧ feedback voltage

CT1, CT2‧‧‧ control signals

Claims (9)

A low-dropout voltage regulator having a voltage output terminal and comprising: a first differential amplifier, generating a first control signal according to a reference voltage and a feedback voltage; and a power switch receiving an input voltage and receiving Controlling the first control signal; an impedance component electrically connected between the power switch and the voltage output terminal; a second differential amplifier electrically connecting the two ends of the impedance component and generating a second control a signal; a feedback circuit determines whether to generate the feedback voltage according to the second control signal; and a signal generation circuit determines whether to generate the reference voltage according to the second control signal. The low-dropout voltage regulator of claim 1, wherein the second differential amplifier has an input offset voltage, and when the voltage output terminal is electrically connected to a load, the second differential amplifier is based on The voltage across the impedance element switches the second control signal to a first level, and when the voltage output is not connected to the load, the second differential amplifier according to the input offset voltage The second control signal is switched to a second level. The low dropout voltage regulator of claim 2, wherein the feedback circuit generates the feedback voltage in response to the second control signal having the first level, and responsive to having the second level The second control signal stops generating the feedback voltage, and the signal generating circuit is responsive to the second control signal having the first level Generating the reference voltage and stopping generating the reference voltage in response to the second control signal having the second level. The low-dropout voltage regulator of claim 2, wherein the feedback circuit comprises: a switch, the first end of which is electrically connected to the voltage output end, and the control end of the switch receives the second control signal; a first resistor electrically connected to the second end of the switch; and a second resistor, the first end of which is electrically connected to the second end of the first resistor, and the second end of the second resistor is electrically Connected to a ground, wherein the feedback circuit turns on the switch in response to the second control signal having the first level to provide the feedback voltage through the second end of the second resistor, and the feedback The circuit is responsive to the second control signal having the second level to not turn the switch to stop providing the feedback voltage. The low-dropout voltage regulator of claim 2, wherein the signal generating circuit comprises: a voltage generator; and a switch, the first end receives the input voltage, and the second end of the switch is electrically connected The voltage generator, the control end of the switch receives the second control signal, wherein the signal generating circuit turns on the switch in response to the second control signal having the first level, so that the voltage generator is based on the The input voltage of the switch generates the reference voltage, and the signal generating circuit does not turn on the switch in response to the second control signal having the second level, so that the voltage generator stops generating The reference voltage. The low-dropout voltage regulator of claim 1, wherein the impedance component is a resistor, and the resistor is electrically connected between the two input terminals of the second differential amplifier. The low-dropout voltage regulator of claim 1, wherein the second differential amplifier comprises: an input stage comprising a first N-type transistor and a second N-type transistor, wherein the first The control terminal of the N-type transistor is used as a positive input terminal of the second differential amplifier, and the control terminal of the second N-type transistor is used as a negative input terminal of the second differential amplifier, and the first N The size of the type of transistor is smaller than the size of the second N-type transistor; an output stage is electrically connected to the first end of the first N-type transistor and the first end of the second N-type transistor, and is configured to provide The second control signal; and a current source electrically connected to the second end of the first N-type transistor and the second end of the second N-type transistor. The low-dropout voltage regulator of claim 7, wherein the output stage comprises: a first P-type transistor, the first end of which is electrically connected to the first end of the first N-type transistor, a second P-type transistor receives a power supply voltage; and a second P-type transistor, the first end of which is electrically connected to the first end of the second N-type transistor, the second P-type transistor Receiving the power supply voltage, the control end of the second P-type transistor is electrically connected to the first end, and the control of the first P-type transistor The terminal is electrically connected to the control end of the second P-type transistor. The low-dropout voltage regulator of claim 7, wherein the current source comprises a third N-type transistor, and the first end of the third N-type transistor is electrically connected to the first N-type a second end of the crystal and a second end of the second N-type transistor, the second end of the third N-type transistor is electrically connected to a ground end, and the control end of the third N-type transistor is first The terminals are electrically connected.